Log visibility change for all fragments.

Bug: 30681771
Test: SettingsUnitTests

Refactor visibility logging from InstrumentedFragment into a mixin. And
apply mixin in remaining fragments.

Change-Id: Ibbb59904336254a3e4bb9e8c7d0b36e5a6bc2622

src/com/android/settings/SettingsPreferenceFragment.java

@@ -45,6 +45,7 @@ import android.view.ViewGroup;
 import android.widget.Button;
 
 import com.android.settings.applications.LayoutPreference;
+import com.android.settings.core.InstrumentedFragment;
 import com.android.settingslib.HelpUtils;
 
 import java.util.UUID;